The work proposed for this project is composed of a number of interrelated investigations concerning the differentiation and regeneration of skeletal muscle. The local anesthetic drug bupivacaine has been shown to produce a rapid degeneration followed by almost complete regeneration of muscle. This model is to be used for detecting the cell type that survives the degeneration to initiate regeneration. The same model of muscle regeneration is to be subjected to chronic stimulation. After denervation regenerating muscle does not differentiate into fiber types. It is hoped to find out whether in the absence of innervation, differentiation can be produced by chronic stimulation. Using muscle fiber cultures further experiments are being carried out on the effects of nerve extracts on the differentiation of muscle and attempts are being made by column separation and iso-electric focussing to further purify the active agent from the nerve extract.